Parallel operation of rotary converters and storage batteries.



A E.-J.BRRG. PARALLEL OPERATION OF ROTARY CONVERTERS AND STORAGE BATTERIES.

APPLIOATIORFILED 811M213, 1907.

91 6,981 Patented Apr. 6, 1909.

if ttg.

. UNITED s ATEsPA NT OFFICE.

' ERNST J. BERG, OF SCHENEOTADY, NEW Yonx, ASSIGNQR To GENERAL R COMPANY, AICORPORATION or YORK. a

PARALLEL OPERATION OF ROTARY CONVERTERS AND STORAGE BATTERIES.

Specification of Letters Patent Patented April 6, 1909.

. Application filed S'eptemberlS, 1907. Serial No. 392,630.

To all whom it may concern:

Be it known that I, ERNST zen of the UnitedStates, residingat Schenectady, county of Schenectady, State of New York, have invented certain'new and useful Improvements in the Parallel Open ationof Rotary Converters and Storage Batteries, of which the following is a specification. I

Thisinventio n relates to a system of elec trical distribution in which the load-circuit 1s supplied with current from a rotary cononly withthe customary shunt field winding and series field winding, but also with an auxiliary field winding which is excited. by the booster. The booster. is series-excited and therefore its potential will vary with the load, and consevrgluently the excitation of the auxiliary field lsimilarly va With an increasing load on the system, the potential of the rotary must decrease in company with that of the storage battery, so that the combined supply of current from these two.

sources, feeding in parallel, may be most This be dim inished,,an(l, therefore, the auxiliary field is excited in opposition to the main .field. On the contrary, when the load is light, the storage battery is charged by the rotary converter, and at this time the excitation of the rotary should be strengthened,

which means that the polarity of the booster must be reversed, in order that the current in the auxiliary field winding may assist that in the main winding.

The accompanying drawing is a diagramof circuits embodying my invention.

A rotary converter 1 is supplied with alternatin -current from the three-phase line 2,

with t e usual reactance coils 3 in the leads 4. The rota has a shunt field winding 5 and a series fi'el winding 6 in circuit with'its direct:

J. BERG, a citi-' current end. 'The load-circuit is shown at 7,

and across these mains is connected a storage ,battery 8. A suitably-driven booster 9 is laced in series with the battery, having a held winding 10 in series with said battery;

The booster also supplies currentto acirouit containing an auxiliary winding 11, connected across the booster brushes and located on .the field frame of the rotary conv'erter shunt windingis usually wound to give an under excitation at low loads or no load, the

result is that a lagging current is produced in the armature, which, owing to the inductance of "the circuit, has the effect of lowering the potential of the direct-current. But when a storage battery forms a part of the supply system, as inthepresent case, it is desirable when the load is low to generate an excess of current for charging the battery. In order- .to do this, the

otential of the charging circuit must be as high as, or higher than usual. The system I have shown and described effects this maintenance of the potential. The storage battery takes the excess of current over what is neededto carry the load on the mains,'and is itself an additional load. The current which flows into the battery energizes the field-winding 10 of the booster,

which is so wound that it raises the potential of the charging current. of the booster-eurrentin' the auxiliary winding 11 is in such ardirection 'that'it acts in conjunction with the main windings to strengthen the excitation of the rotary and thus maintain the potential on the load-cih cuit.- But when the load becomes heavier, the battery Will begin to dischargeand assist the rotary to carry'the load. As the direction of the discharging current is op osite to" that of the charging current, the po arity of the booster will be reversed, so that the coil 1 1 will operate in opposition to the maln 'wind' .ings and produce a decrease in the excitation of the rotary. As the load increases, and the flow of current from the battery is correspondin 1y increased, the booster-current in theau iary coil becomes stronger, and the decrease inexcitation of the rota becomes greater, so that the potential oi the directcurrent generated by the rotary gradually 20. appears, therefore, that by my invention-I field in case of light load on the distributing 45 current source to insure charging of the bat- 50 Q 3,- The combination of a source of current diminishes as the load increases; a result I which corresponds with the action of the storage battery. The rotary and the battery thus operate harmoniously in caring for the 5 increasing load. Inasmuch, however, as the booster depends u on the storage battery for its excitation, an as the magnetism in the poles and therefore its voltage is limited, the counter-excitation of the main field cannot exceed a certain value. If, therefore, the demand upon the system exceeds the maximum which the battery can give without mechanical damage, the excess load must be carried by the rotary. As soon as this point 5 is reached, the excitation of the main field will begin to strengthen, and'since a stronger field means a more leading or less lagging current in the armature, the potential of the direct-eurrent will begin to rise slightly. It

rovide for, first, charging the battery on a light load, second, operatin the battery and rotary in parallel to care 'or an increasing load up to a given point, and third, relieving 25. the battery automatically from such excessive load as would cause mechanical damage.

What I claim as new and desire to secure' by Letters Patent of the United States, is

1. The combination of a source of current having a main field winding, a direct-current distributing circuit, a storage battery connected across said circuit, a booster in. series with said battery, and an auxiliary winding for said source in circuit with said booster,

said winding acting to strengthen the main "circuit, but weakening said field in case of a heavy load on said distributing circuit. 2. The combination of a source of current 0 having a main field winding, a direct-current distributing circuit receiving energy therefrom, a storage battery, and a booster in circuit with said storage battery and cooperating with an auxiliary field winding on said tery when the load on the distributing circuit is light and to, prevent excessive discharge from the battery when the load on the distributing circuit becomes heavy.

having a main field winding and anauxiliary field winding, a distributing circuit receiving energy from said source, a 'storage battery connected across said distributing circuit and 5 means cooperating with said battery and said auxiliary winding to insure charging of the battery when the load on the d stributmg circuit is light and to prevent excessive dis charge from the battery at all times.

4. The combination with an alternatingcurrent supply system, of a rotary converter,

a direct-current distributing system, a storage battery connected with said direct cun rent s stern, and means for causing the potentia of the rotary to decrease with that of the battery when both are operating in.

parallel.

5. The combination with an alternatingcurrent supply system, of a rotary converter, a direct-current distributing system, a storage battery connected across the direct-cur rent mains, a booster in series with said battery, and an auxiliary field winding on the rotary in circuit with said booster.

6. The combination with an alternatingcurrent supply system, of a rotary converter, a direct-current distributing system, a-storage battery .connected'across the direct-current mains, a booster in series with said battery, and an auxiliary field winding on the above acertain value.

9. The combination with a rotary eonverter, of a storage battery adapted to operate in parallel therewith, and means for strengthening the excitation of the field of the rotary on a light load to provide current for charging the battery..

10. The combination with a rotary converter, of a storage battery adapted to operate in parallel therewith, a booster in series with said battery, and means for varying the excitation of the field of the rotary in accordance with the direction of the fiow of current in said battery circuit.

in witness whereof, I have hereunto set my hand this 11th day of September, 1907.

ERNST -J. BERG.

Witnesses BENJAMIN B. HULL, BERTHA- SECOR, 

